One of the larger costs in the airline industry is the cost of fuel. Currently companies in the airline industry run on very slim profit margins. Management of any company, including the companies in the airline industry, knows that containing or reducing costs generally will yield higher profits. In addition to increasing company profits, if fuel can be saved in the aircraft industry it is good for the earth and the environment. Fossil fuels are being used at increasing rates around the world. World reserves of fossil fuels are limited. So, it is advantageous to conserve as much fuel as possible so as to extend the life of world reserves. This provides added time for development of alternative means of energy.
Currently aircraft manufacturers and/or airlines set forth instructions or protocols that include many aspects of the operations of an aircraft including preflight procedures, departure procedures, shut down procedures, and procedures for securing the aircraft. The procedures are very detailed and airline pilots and other professional pilots are generally taught to follow these procedures very closely. Procedure manuals, such as an aircraft operating manual, and a cockpit operating manual, detail procedures for start, taxiing, take off, climb, cruise, descent, approach and landing. The current protocol for descent from cruising altitude to about 11,000-9,000 feet generally instructs pilots to set the engine at idle speed during the descent. One of the parameters that is measured and monitored for some airliner procedures is the engine pressure ratio (EPR). The EPR is defined to be the total pressure ratio across the engine. Thus, the EPR is the ratio of the pressure at the exhaust of a turbojet engine to the pressure measured at the front face of the turbojet engine. A first pressure sensor is placed at the front face of a turbojet engine, and a second pressure sensor is placed at the exhaust of the turbojet engine. Given these two pressures, the EPR can be easily determined for an operating engine and displayed to the pilot on a cockpit dial. The EPR is a parameter that is monitored by a pilot during certain maneuvers. For example for one type of aircraft, the EPR during takeoff is monitored so that it stays at approximately 2.1. Of course, this EPR setting changes for different types of aircraft, different engines, different environmental conditions (such as weather), and can also changes as a function of the weight of the aircraft. While cruising, the EPR varies as a function of altitude, temperature, weight and type of engine. In many aircraft the EPR is monitored during many of the various procedures of the aircraft. In other aircraft, the EPR is not monitored and the EPR is not a parameter that is referred to during various procedures. However, the same factors that affect the EPR still affects the operations of the aircraft.
During descent from altitude, the protocol is to place the turbojet in an idle mode. During the idle mode, at about flight level 330 (33,000 feet)+the EPR corresponding to idle mode is approximately 0.8. This means that the pressure at the front of the turbojet is higher than the pressure at the exhaust of the turbojet. As a result, the engine acts as a speed brake during at least a portion of the descent. As the aircraft descends the air gets more dense. The result is that the EPR rises as the aircraft descends. In many instances the EPR may be near 1.0 at 10,000 feet. Of course this can vary based on the atmospheric pressure at any given time. However, during the time when the EPR is less than 1.0, the engine acts as a speed brake with as much as 0.3 to 63 square feet or more of frontage. With the engine acting as a speed brake, the descent takes longer and wastes jet fuel. Most procedures require a pilot to throttle back to idle during the descent. If an entire fleet of airliners follow such a procedure for descent, the amount of fuel waste is significant. Of course, when fuel costs are high, fuel expense is also high.
The description set out herein illustrates the various embodiments of the invention, and such description is not intended to be construed as limiting in any manner.